1. Field of the Invention
The present invention relates to a process for producing hydrogen peroxide. Furthermore this invention relates to a process for producing hydrogen peroxide by reacting hydrogen and oxygen directly.
2. Description of the Related Art
Hydrogen peroxide is one of the most important industrial products having wide variety of uses, such as bleaching agents (for papers/pulps and natural fibers), industrial chemicals (oxidizing agents, plasticizers, rubber chemicals, and reducing agents for pollution processing), medical supplies (oxidizing agent), foods (bleaching sterilization agents for processed marine products, other various bleaching agents) and the like.
At present, the most general process for industrial production of hydrogen peroxide is the autoxidation which uses alkyl anthraquinone. However, the process needs many steps, such as reduction and oxidation of alkyl anthraquinone, and extraction separation, purification and concentration of hydrogen peroxide produced, and the process becomes complicated. Moreover, loss of alkyl anthraquinone and degradation of a reduction catalyst, etc. have been a problem.
In order to solve these problems, conventionally, hydrogen and oxygen are contacted in an aqueous medium in the presence of a platinum group metal supported catalyst to produce hydrogen peroxide directly. (JP-B 55-18646, JP-B 56-47121, JP-B 1-23401, JP-A63-156005, etc.). In the process, it has been used a solution to which acid and inorganic salt is added as a reaction medium.
For example, JP-A 63-156005 describes that hydrogen peroxide is produced in high concentration using a metal catalyst supporting a platinum group metal on a support material, by reacting hydrogen and oxygen in aqueous medium under a high pressure condition. In the process, however, it is necessary to add an acid in high concentration, and to add a compound which dissociates to generate halogen ion, for example, sodium bromide.
JP-A 57-92506 describes that ketone, ether, ester, amide, etc. can be used as a reaction medium, and methanol is excellent among them. However, the catalyst system used here is a metal supporting a platinum group metal on a support material, an acid, and a halogen ion. And to depress the decomposition of hydrogen peroxide, it is necessary to make formaldehyde exist together in methanol. Therefore, the process requires the step of adding these compounds, and in some cases the step of removing formaldehyde, and becomes disadvantageous industrially.